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EMISSION MECHANISM OF “GREEN FUZZIES” IN HIGH-MASS STAR-FORMING REGIONS
Takami, Michihiro,Chen, How-Huan,Karr, Jennifer L.,Lee, Hsu-Tai,Lai, Shih-Ping,Minh, Young-Chol IOP Publishing 2012 The Astrophysical journal Vol.748 No.1
<P>The Infrared Array Camera (IRAC) on the Spitzer Space Telescope has revealed that a number of high- mass protostars are associated with extended mid- infrared emission, particularly prominent at 4.5 mu m. These are called 'Green Fuzzy' emission or 'Extended Green Objects.' We present color analysis of this emission toward six nearby (d = 2- 3 kpc) well- studied high- mass protostars and three candidate high- mass protostars identified with the Spitzer GLIMPSE survey. In our color- color diagrams, most of the sources show a positive correlation between the [3.6]-[4.5] and [3.5]-[5.8] colors along the extinction vector in all or part of the region. We compare the colors with those of scattered continuum associated with the low- mass protostar L 1527, modeled scattered continuum in cavities, shocked emission associated with low- mass protostars, modeled H2 emission for thermal and fluorescent cases, and modeled polycyclic aromatic hydrocarbon (PAH) emission. Of the emission mechanisms discussed above, scattered continuum provides the simplest explanation for the observed linear correlation. In this case, the color variation within each object is attributed to different foreground extinctions at different positions. Alternative possible emission mechanisms to explain this correlation may be a combination of thermal and fluorescent H2 emission in shocks, and a combination of scattered continuum and thermal H2 emission, but detailed models or spectroscopic follow- up are required to investigate this possibility further. Our color- color diagrams also show possible contributions from PAHs in two objects. However, none of our samples show clear evidence for PAH emission directly associated with the high- mass protostars, several of which should be associated with ionizing radiation. This suggests that these protostars are heavily embedded even at mid- infrared wavelengths.</P>
First Results from BISTRO: A SCUBA-2 Polarimeter Survey of the Gould Belt
Ward-Thompson, Derek,Pattle, Kate,Bastien, Pierre,Furuya, Ray S.,Kwon, Woojin,Lai, Shih-Ping,Qiu, Keping,Berry, David,Choi, Minho,Coudé,, Simon,Francesco, James Di,Hoang, Thiem,Franzmann, Erica American Astronomical Society 2017 The Astrophysical Journal Vol.842 No.1
<P>We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array. 2 camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope in Hawaii. We discuss the survey's aims and objectives. We describe the rationale behind the survey, and the questions that. the survey will aim to answer. The most important of these is the role of magnetic fields in the star formation process on the scale of individual filaments and cores in dense regions. We describe the data acquisition and reduction processes for POL-2, demonstrating both repeatability and consistency with previous data. We present a first-look analysis of the first results from the BISTRO survey in the OMC 1 region. We see that the magnetic field lies approximately perpendicular to the famous 'integral filament' in the densest regions of that filament. Furthermore, we see an 'hourglass' magnetic field morphology extending beyond the densest region of the integral filament into the less-dense surrounding material, and discuss possible causes for this. We also discuss the more complex morphology seen along the Orion Bar region. We examine the morphology of the field along the lower-density northeastern filament. We find consistency with previous theoretical models that predict magnetic fields lying parallel to low-density, non-self-gravitating filaments, and perpendicular to higher-density, self-gravitating filaments.</P>